1. Field of the Invention
The present invention relates to a modular RF terminal and, more particularly, to a miniature terminal including discrete, reconfigurable modules interconnected by high-density analog and digital busses for distributing communication, navigation, sensing and control data among the modules.
2. Description of the Related Art
In digital devices that generate and process RF signals, such as modern transceivers, it is beneficial to minimize the size, weight, power consumption and cost. For example, such goals are required for the equipment to be used in the Earth Science Enterprise (ESE) mission through which NASA is engaged in the exploration of Earth, with the goal of understanding and predicting natural phenomena, and the interconnection of atmosphere, oceans, continents, and living ecosystems. More particularly, this exploration is intended to develop a scientific understanding of the Earth system and its response to natural or human-induced changes to enable improved prediction of climate, weather and natural hazards, which may lead ultimately to an improved quality of life and sustained habitability of the Earth. The Advanced Component Technology (ACT) Program sets forth two objectives for technology that supports the ESE mission. First, new electronic systems must address risk, cost, size, and development time reduction while spanning instrumentation, varying platforms, and information systems. Second, new electronic systems must truly be enablers for new forms of Earth measurements and observations, including surface, space-borne, and airborne measurements.
Such systems require transceiver capabilities to support communications, navigation and/or processing of sensor data. Depending on particular mission requirements, there may be a need to support communications that include air or space to ground communications, satellite cross-link communications, and data relay. Navigation requirements may include position/time determination and absolute/relative navigation. Examples of sensing that may require support include: ocean topography measurement, ocean surface wind measurement, occulation measurement, measurement of topography and surface changes, soil moisture and salinity, and global precipitation. In some cases, the system electronics must be able to support a phased array antenna having numerous discrete transmit/receive elements capable of electronic beam forming and steering and requiring separate corresponding transmit and receive channels.
To meet these objectives and system requirements, there has been an effort to develop electronics suitable for airborne and space-borne systems that perform multiple functions while having reduced size, weight, power and cost relative to existing systems. However, miniaturization of RF and transceiver components and packaging cannot be realized without overcoming a number of technical obstacles. For example, practical problems such as heat dissipation, the placement and size of external connectors, and the layout of circuit boards and positioning of internal components must be addressed. One particularly difficult problem that arises with attempts to minimize transceiver size is how to reduce the amount of space required for wiring and signal conductors that convey signals to various analog and digital processing circuitry within the transceiver.
In modern transceivers and most electronic devices of a digital nature, digital busses pass multi-bit (e.g., sixteen bit, thirty-two bit, etc.) digital samples through the system. If the system must support multiple signals simultaneously, additional sets of discrete signal conductors must be added, or the multiple signals must be passed over the same digital bus in a time-shared manner. To achieve a compact transceiver design, the number of signal conductors should be minimized to the greatest extent possible; thus, bus time sharing is a more viable option with miniaturization. However, every digital bus has a maximum speed of operation, and time sharing among multiple signals effectively reduces the throughput supported by the bus with respect to individual signals. Depending on whether the digital signals are eight bits, sixteen bits, thirty-two bits, etc., this problem expands with the number of bits of the digital signals. Thus, signal bus requirements can become a major impediment to reducing the size of electronic devices that digitally process RF signals. In a practical context, the problem of digital bussing becomes unmanageable when attempting to develop a reduced-size RF transceiver capable of supporting a phased-array antenna, since each antenna element transmits and receives separate RF signals, each of which involves processing of multi-bit digital samples.
More generally, given the variety of sensing, communication and navigation capabilities required throughout a complex, multifunctional system, such as that contemplated by the ESE mission, there are considerable risks associated with development time, development, equipment and operational costs, and system reliability. Thus, development of an architecture that addresses these risks would be desirable.